1. Field of the Invention
The invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method in which color processing is performed.
2. Description of the Related Art
In a color printer which inputs R (red), G (green) and B (blue) signals, or C (cyan), M (magenta) and Y (yellow) signals or C, M, Y and K (black) signals, serving as complementary-color signals of the R, G and B signals, and which prints an image in colors corresponding to the input signals with ink or toner having C, M and Y, or C, M, Y and K colors, in order to print a blue color, a cyan (C) component having a density of 100% and a magenta (M) component having a density of 100% are superposed.
Such a technique, however, has the following problems.
That is, in a binary color printing processing apparatus, binary-coding processing, such as dither processing, density diffusion processing or the like, is performed for multivalue density data comprising a plurality of color components. In this processing, each of a plurality of color components is convereted to binary density data by being compared with a predetermined threshold. Hence, in the above-described printing method, a high-density image is, in some cases, formed for a low-density portion.
Accordingly, in primary-color and secondary-color regions (R, G, B, C, M and Y regions) where the level of certain color component data is lower than the levels of color component data in the vicinity thereof, the color component whose level must be low is output with a high level in a color different from the colors of adjacent pixels in a part of the image. Hence, the color output with a high level is pronounced with respect to colors of adjacent pixels which are reproduced in an excellent state. As a result, a grainy image is produced.
Furthermore, when an ideal subtractive color mixture cannot be performed, a color obtained by mixing 100% cyan and magenta differs from the expected blue, and is output in a color tending to purple.